Perceptual preprocessing techniques to reduce complexity of video coders

Abstract

A method of encoding a video sequence including a sequence of video images includes comparing elements of a portion of a first video image with elements of a portion of a second video image to generate respective intensity difference values for the element comparisons. Then, a first value is assigned to the intensity difference values that are at least above a visually perceptible threshold value and a second value is assigned to the intensity difference values that are not at least above the visually perceptible threshold value. Next, the method includes dividing the portion of the first video image into sub-portions and summing the first and second values associated with each corresponding sub-portion to generate respective sums. If a respective sum is at least greater than a decision value, a variable associated with that sub-portion is set to a first value. If a respective sum is not at least greater than the decision value, the variable associated with that sub-portion is set to a second value. The values associated with the variables are then added. Depending on the result of the addition, the portion of the first video image is either motion compensated or not.

What is claimed is:  
     
       1. A method of encoding a video sequence including a sequence of video images, the method comprising the steps of: 
       comparing elements of a portion of a first video image with elements of a portion of a second video image such that each element from the portion of the first video image that results in a difference value that is at least greater than a perceptual threshold is identified and the number of such elements is added to generate a sum, the perceptual threshold being a function of a quantization parameter associated with a bit rate of the video sequence; and  
       comparing the sum to a decision value such that the portion of the first video image is encoded when the sum is at least greater than the decision value;  
       wherein the perceptual threshold is equivalent to the sum of a just-noticeable-distortion threshold and the quantization parameter.  
     
     
       2. The method of  claim 1 , wherein the first video image is a current frame of the video sequence. 
     
     
       3. The method of  claim 1 , wherein the second video image is a previous frame of the video sequence. 
     
     
       4. The method of  claim 1 , wherein the respective portions of the first and second video images compared are macroblocks. 
     
     
       5. The method of  claim 1 , wherein the decision value is zero. 
     
     
       6. The method of  claim 1 , wherein the decision value is non-zero. 
     
     
       7. The method of  claim 1 , wherein the difference value is an intensity difference value. 
     
     
       8. The method of  claim 1 , wherein encoding the portion of the first video image when the sum is at least greater than the decision value includes motion compensation. 
     
     
       9. The method of  claim 1 , wherein the quantization parameter is multiplied by a scaling constant. 
     
     
       10. Apparatus for encoding a video sequence including a sequence of video images, comprising: 
       a processor for comparing elements of a portion of a first video image with elements of a portion of a second video image such that each element from the portion of the first video image that results in a difference value that is at least greater than a perceptual threshold is identified and the number of such elements is added to generate a sum, the perceptual threshold being a function of a quantization parameter associated with a bit rate of the video sequence, the processor also for comparing the sum to a decision value such that a signal is generated by the processor representing the result of the second comparison; and  
       an encoder coupled to the processor for encoding the portion of the first video image when the signal received from the processor indicates that the sum is at least greater than the decision value;  
       wherein the perceptual threshold is equivalent to the sum of a just-noticeable-distortion threshold and the quantization parameter.  
     
     
       11. The apparatus of  claim 10 , wherein the first video image is a current frame of the video sequence. 
     
     
       12. The apparatus of  claim 10 , wherein the second video image is a previous frame of the video sequence. 
     
     
       13. The apparatus of  claim 10 , wherein the respective portions of the first and second video images compared are macroblocks. 
     
     
       14. The apparatus of  claim 10 , wherein the decision value is zero. 
     
     
       15. The apparatus of  claim 10 , wherein the decision value is non-zero. 
     
     
       16. The apparatus of  claim 10 , wherein the difference value is an intensity difference value. 
     
     
       17. The apparatus of  claim 10 , wherein the encoding performed by the encoder includes motion compensation. 
     
     
       18. The apparatus of  claim 10 , wherein the quantization parameter is multiplied by a scaling constant. 
     
     
       19. A method of encoding a video sequence including a sequence of video images, the method comprising the steps of: 
       comparing elements of a portion of a first video image with elements of a portion of a second video image such that each element from the portion of the first video image that results in a difference value that is at least greater than a perceptual threshold is identified;  
       dividing the portion of the first video image into sub-portions such that the number of elements that result in a difference value that is at least greater than the perceptual threshold is added to generate a sum for each sub-portion, each sub-portion sum being compared to a sub-portion decision value and assigned a value based on the comparison; and  
       adding the values assigned to the sub-portions such that the portion of the first video image is encoded based on the result of the addition;  
       wherein the perceptual threshold is a function of a quantization parameter associated with a bit rate of the video sequence, and further wherein the perceptual threshold is equivalent to the sum of a just-noticeable-distortion threshold and the quantization parameter.  
     
     
       20. The method of  claim 19 , wherein the first video image is a current frame of the video sequence. 
     
     
       21. The method of  claim 19 , wherein the second video image is a previous frame of the video sequence. 
     
     
       22. The method of  claim 19 , wherein the respective portions of the first and second video images compared are macroblocks. 
     
     
       23. The method of  claim 19 , wherein the sub-portions are sub-blocks of a macroblock such that the union of the sub-blocks equals the macroblock. 
     
     
       24. The method of  claim 19 , wherein a sub-portion sum is assigned a value of logic zero if the sub-portion sum is at least greater than the sub-portion decision value and a value of logic one otherwise. 
     
     
       25. The method of  claim 24 , wherein the adding step is a logical addition operation such that a result of logic zero indicates that the portion of the first video image is to be encoded and a result of logic one indicates that the portion of the first video image is not to be encoded. 
     
     
       26. The method of  claim 19 , wherein the difference value is an intensity difference value. 
     
     
       27. The method of  claim 19 , wherein encoding the portion of the first video image includes motion compensation. 
     
     
       28. The method of  claim 19 , wherein the quantization parameter is multiplied by a scaling constant. 
     
     
       29. Apparatus for encoding a video sequence including a sequence of video images, comprising: 
       a processor for comparing elements of a portion of a first video image with elements of a portion of a second video image such that each element from the portion of the first video image that results in a difference value that is at least greater than a perceptual threshold is identified, dividing the portion of the first video image into sub-portions such that the number of elements that result in a difference value that is at least greater than the perceptual threshold is added to generate a sum for each sub-portion, each sub-portion sum being compared to a sub-portion decision value and assigned a value based on the comparison, and adding the values assigned to the sub-portions; and  
       an encoder for encoding the portion of the first video image based on the result of the addition;  
       wherein the perceptual threshold is a function of a quantization parameter associated with a bit rate of the video sequence, and further wherein the perceptual threshold is equivalent to the sum of a just-noticeable-distortion threshold and the quantization parameter.  
     
     
       30. The apparatus of  claim 29 , wherein the first video image is a current frame of the video sequence. 
     
     
       31. The apparatus of  claim 29 , wherein the second video image is a previous frame of the video sequence. 
     
     
       32. The apparatus of  claim 29 , wherein the respective portions of the first and second video images compared are macroblocks. 
     
     
       33. The apparatus of  claim 29 , wherein the sub-portions are sub-blocks of a macroblock such that the union of the sub-blocks equals the macroblock. 
     
     
       34. The apparatus of  claim 29 , wherein a sub-portion sum is assigned a value of logic zero if the sub-portion sum is at least greater than the sub-portion decision value and a value of logic one otherwise. 
     
     
       35. The apparatus of  claim 34 , wherein the adding step performed by the processor is a logical addition operation such that a result of logic zero indicates that the portion of the first video image is to be encoded and a result of logic one indicates that the portion of the first video image is not to be encoded. 
     
     
       36. The apparatus of  claim 29 , wherein the difference value is an intensity difference value. 
     
     
       37. The apparatus of  claim 29 , wherein the encoding performed by the encoder includes motion compensation. 
     
     
       38. The apparatus of  claim 29 , wherein the quantization parameter is multiplied by a scaling constant.